I’m curious why you are replacing all the old doors. Is this an aesthetics thing? They can’t be painted?
For the furnace door, you probably need a fire-rated door. Finding that information can always be tricky. Calling townhall can open up a can of worms. Asking at a big box store, you’ll get a bunch of clueless workers.
We are replacing the doors because, currently, we have a bunch of cheap, flat, hollow-cored doors that look terrible. We wanted to upgrade to some nicer doors. Both rooms currently have hollow-core doors with a small Louvered panel at the bottom.
Gotcha. I definitely do recommend solid core doors. The flippers I bought my place from made a lot of questionable choices, mostly driven by saving a buck, but they did install solid core doors everywhere and it makes a big difference.